Pathogens and the body's barriers to infection (Edexcel Int. A-level Biology)

This fully-resourced lesson describes the major routes that pathogens take when entering the body and the body’s barriers to this infection. The engaging and detailed PowerPoint and accompanying resources have been designed to cover points 6.7 (i) & (ii) of the Edexcel International A-level Biology specification and includes descriptions of the following barriers:

• skin
• the blood clotting process
• mucous membranes
• stomach acid
• vaginal acid and flora
• skin and gut flora
• wax in the ear canal

There are clear links to topics 1, 2 and 3 in each of these barriers, so these are considered and discussed during each of the descriptions. For example, the presence of keratin in the cytoplasm of the skin cells allows the student knowledge of the properties of this fibrous protein to be checked. Other topics that are revisited during this lesson include protein structure, key terminology and the epithelium that lines the different parts of the airways.

All of the exam-style questions have mark schemes that are embedded into the PowerPoint and a number of the tasks have been differentiated to allow students of differing abilities to access the work.